The CDC is warning clinicians that a rare enterovirus caused six clusters of respiratory illness -- including several deaths -- from 2008 to 2011.

Action Points

Explain that the CDC is warning clinicians that a rare enterovirus (human enterovirus 68 [HEV68]) caused six clusters of respiratory illness – including several deaths – from 2008 to 2011.

Note that children were disproportionately affected in the six enterovirus clusters identified by the CDC, with 77 of 95 total cases occurring in patients 19 or younger.

The CDC is warning clinicians that a rare enterovirus caused six clusters of respiratory illness – including several deaths – from 2008 to 2011.

Three of the clusters, involving 39 people, occurred in the U.S., the agency said in the Sept. 30 issue of Morbidity and Mortality Weekly Report; another 56 people were affected in Asia and Europe.

More than half of the cases in the six clusters occurred in children under age 5.

The pathogen is human enterovirus 68 (HEV68), which has epidemiological and biological similarities to human rhinoviruses. It was first isolated in 1962 and has been reported only rarely since then, the CDC said.

"Identification of a large number of patients with HEV68 respiratory disease detected during a single season," the CDC noted, "is a recent phenomenon."

The six clusters suggest that physicians should be aware that the pathogen can be among the causes of viral respiratory disease, the CDC reported, adding that clusters of unexplained respiratory illness should be reported to appropriate public health authorities.

The outbreaks, in order of appearance, were:

In the Philippines, from October 2008 through March 2009, among pediatric patients hospitalized with pneumonia. Samples from 816 patients were screened using molecular methods, and 21 (or 2.6%) were found to be HEV68.

A pediatric hospital in Philadelphia reported 28 cases from August through October 2009.

A hospital in Atlanta found six cases from September 2009 through April 2010.

In Japan, authorities reported a large number of cases of HEV68 in 2010, but clinical and demographic data were available for only a subset of 11 pediatric patients.

During August and September 2010, officials at a rural hospital in Arizona faced a significant increase in pediatric admissions for lower respiratory tract illness. No pathogen was immediately detected, but nasopharyngeal specimens from seven patients were sent to CDC for further testing and HEV68 was identified in five.

Finally, from August through November 2010, HEV68 was found in a prospective, hospital-based study of respiratory infections in the Netherlands. Specimens from 24 patients with acute respiratory illness were positive for HEV68.

Although most cases in the six clusters involved respiratory illness, "the full spectrum of illness that (HEV68) can cause is unknown," the agency noted.

Of the 95 cases, 77 were in patients 19 or younger, with 54 among children under 5, 11 among those 5 through 9, and 12 among those 10 through 19.

Illness was often severe -- among the 24 Dutch patients, for instance, 23 were hospitalized during their illness and five needed intensive care.

There were also three deaths – two children in the Philippines and a boy in Japan.

The CDC cautioned that it is not known if the increase in reported cases arises because of better detection methods or because of the emergence of pathogen.